text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2020 The Bitcoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifndef BITCOIN_NET_H
  #define BITCOIN_NET_H
  
  #include <addrdb.h>
  #include <addrman.h>
  #include <amount.h>
  #include <bloom.h>
  #include <compat.h>
  #include <crypto/siphash.h>
  #include <hash.h>
  #include <limitedmap.h>
  #include <netaddress.h>
  #include <net_permissions.h>
  #include <policy/feerate.h>
  #include <protocol.h>
  #include <random.h>
  #include <streams.h>
  #include <sync.h>
  #include <threadinterrupt.h>
  #include <uint256.h>
  
  #include <atomic>
  #include <deque>
  #include <stdint.h>
  #include <thread>
  #include <memory>
  #include <condition_variable>
  
  #ifndef WIN32
  #include <arpa/inet.h>
  #endif
  
  
  class CScheduler;
  class CNode;
  class BanMan;
  struct bilingual_str;
  
  /** Default for -whitelistrelay. */
  static const bool DEFAULT_WHITELISTRELAY = true;
  /** Default for -whitelistforcerelay. */
  static const bool DEFAULT_WHITELISTFORCERELAY = false;
  
  /** Time after which to disconnect, after waiting for a ping response (or inactivity). */
  static const int TIMEOUT_INTERVAL = 20 * 60;
  /** Run the feeler connection loop once every 2 minutes or 120 seconds. **/
  static const int FEELER_INTERVAL = 120;
  /** The maximum number of new addresses to accumulate before announcing. */
  static const unsigned int MAX_ADDR_TO_SEND = 1000;
  /** Maximum length of incoming protocol messages (no message over 4 MB is currently acceptable). */
  static const unsigned int MAX_PROTOCOL_MESSAGE_LENGTH = 4 * 1000 * 1000;
  /** Maximum length of the user agent string in `version` message */
  static const unsigned int MAX_SUBVERSION_LENGTH = 256;
  /** Maximum number of automatic outgoing nodes over which we'll relay everything (blocks, tx, addrs, etc) */
  static const int MAX_OUTBOUND_FULL_RELAY_CONNECTIONS = 8;
  /** Maximum number of addnode outgoing nodes */
  static const int MAX_ADDNODE_CONNECTIONS = 8;
  /** Maximum number of block-relay-only outgoing connections */
  static const int MAX_BLOCKS_ONLY_CONNECTIONS = 2;
  /** -listen default */
  static const bool DEFAULT_LISTEN = true;
  /** -upnp default */
  #ifdef USE_UPNP
  static const bool DEFAULT_UPNP = USE_UPNP;
  #else
  static const bool DEFAULT_UPNP = false;
  #endif
  /** The maximum number of peer connections to maintain. */
  static const unsigned int DEFAULT_MAX_PEER_CONNECTIONS = 125;
  /** The default for -maxuploadtarget. 0 = Unlimited */
  static const uint64_t DEFAULT_MAX_UPLOAD_TARGET = 0;
  /** The default timeframe for -maxuploadtarget. 1 day. */
  static const uint64_t MAX_UPLOAD_TIMEFRAME = 60 * 60 * 24;
  /** Default for blocks only*/
  static const bool DEFAULT_BLOCKSONLY = false;
  /** -peertimeout default */
  static const int64_t DEFAULT_PEER_CONNECT_TIMEOUT = 60;
  
  static const bool DEFAULT_FORCEDNSSEED = false;
  static const size_t DEFAULT_MAXRECEIVEBUFFER = 5 * 1000;
  static const size_t DEFAULT_MAXSENDBUFFER    = 1 * 1000;
  
  typedef int64_t NodeId;
  
  struct AddedNodeInfo
  {
      std::string strAddedNode;
      CService resolvedAddress;
      bool fConnected;
      bool fInbound;
  };
  
  class CNodeStats;
  class CClientUIInterface;
  
  struct CSerializedNetMsg
  {
      CSerializedNetMsg() = default;
      CSerializedNetMsg(CSerializedNetMsg&&) = default;
      CSerializedNetMsg& operator=(CSerializedNetMsg&&) = default;
      // No copying, only moves.
      CSerializedNetMsg(const CSerializedNetMsg& msg) = delete;
      CSerializedNetMsg& operator=(const CSerializedNetMsg&) = delete;
  
      std::vector<unsigned char> data;
      std::string command;
  };
  
  
  class NetEventsInterface;
  class CConnman
  {
  public:
  
      enum NumConnections {
          CONNECTIONS_NONE = 0,
          CONNECTIONS_IN = (1U << 0),
          CONNECTIONS_OUT = (1U << 1),
          CONNECTIONS_ALL = (CONNECTIONS_IN | CONNECTIONS_OUT),
      };
  
      struct Options
      {
          ServiceFlags nLocalServices = NODE_NONE;
          int nMaxConnections = 0;
          int m_max_outbound_full_relay = 0;
          int m_max_outbound_block_relay = 0;
          int nMaxAddnode = 0;
          int nMaxFeeler = 0;
          int nBestHeight = 0;
          CClientUIInterface* uiInterface = nullptr;
          NetEventsInterface* m_msgproc = nullptr;
          BanMan* m_banman = nullptr;
          unsigned int nSendBufferMaxSize = 0;
          unsigned int nReceiveFloodSize = 0;
          uint64_t nMaxOutboundTimeframe = 0;
          uint64_t nMaxOutboundLimit = 0;
          int64_t m_peer_connect_timeout = DEFAULT_PEER_CONNECT_TIMEOUT;
          std::vector<std::string> vSeedNodes;
          std::vector<NetWhitelistPermissions> vWhitelistedRange;
          std::vector<NetWhitebindPermissions> vWhiteBinds;
          std::vector<CService> vBinds;
          bool m_use_addrman_outgoing = true;
          std::vector<std::string> m_specified_outgoing;
          std::vector<std::string> m_added_nodes;
          std::vector<bool> m_asmap;
      };
  
      void Init(const Options& connOptions) {
          nLocalServices = connOptions.nLocalServices;
          nMaxConnections = connOptions.nMaxConnections;
          m_max_outbound_full_relay = std::min(connOptions.m_max_outbound_full_relay, connOptions.nMaxConnections);
          m_max_outbound_block_relay = connOptions.m_max_outbound_block_relay;
          m_use_addrman_outgoing = connOptions.m_use_addrman_outgoing;
          nMaxAddnode = connOptions.nMaxAddnode;
          nMaxFeeler = connOptions.nMaxFeeler;
          m_max_outbound = m_max_outbound_full_relay + m_max_outbound_block_relay + nMaxFeeler;
          nBestHeight = connOptions.nBestHeight;
          clientInterface = connOptions.uiInterface;
          m_banman = connOptions.m_banman;
          m_msgproc = connOptions.m_msgproc;
          nSendBufferMaxSize = connOptions.nSendBufferMaxSize;
          nReceiveFloodSize = connOptions.nReceiveFloodSize;
          m_peer_connect_timeout = connOptions.m_peer_connect_timeout;
          {
              LOCK(cs_totalBytesSent);
              nMaxOutboundTimeframe = connOptions.nMaxOutboundTimeframe;
              nMaxOutboundLimit = connOptions.nMaxOutboundLimit;
          }
          vWhitelistedRange = connOptions.vWhitelistedRange;
          {
              LOCK(cs_vAddedNodes);
              vAddedNodes = connOptions.m_added_nodes;
          }
      }
  
      CConnman(uint64_t seed0, uint64_t seed1);
      ~CConnman();
      bool Start(CScheduler& scheduler, const Options& options);
  
      void StopThreads();
      void StopNodes();
      void Stop()
      {
          StopThreads();
          StopNodes();
      };
  
      void Interrupt();
      bool GetNetworkActive() const { return fNetworkActive; };
      bool GetUseAddrmanOutgoing() const { return m_use_addrman_outgoing; };
      void SetNetworkActive(bool active);
      void OpenNetworkConnection(const CAddress& addrConnect, bool fCountFailure, CSemaphoreGrant *grantOutbound = nullptr, const char *strDest = nullptr, bool fOneShot = false, bool fFeeler = false, bool manual_connection = false, bool block_relay_only = false);
      bool CheckIncomingNonce(uint64_t nonce);
  
      bool ForNode(NodeId id, std::function<bool(CNode* pnode)> func);
  
      void PushMessage(CNode* pnode, CSerializedNetMsg&& msg);
  
      template<typename Callable>
      void ForEachNode(Callable&& func)
      {
          LOCK(cs_vNodes);
          for (auto&& node : vNodes) {
              if (NodeFullyConnected(node))
                  func(node);
          }
      };
  
      template<typename Callable>
      void ForEachNode(Callable&& func) const
      {
          LOCK(cs_vNodes);
          for (auto&& node : vNodes) {
              if (NodeFullyConnected(node))
                  func(node);
          }
      };
  
      template<typename Callable, typename CallableAfter>
      void ForEachNodeThen(Callable&& pre, CallableAfter&& post)
      {
          LOCK(cs_vNodes);
          for (auto&& node : vNodes) {
              if (NodeFullyConnected(node))
                  pre(node);
          }
          post();
      };
  
      template<typename Callable, typename CallableAfter>
      void ForEachNodeThen(Callable&& pre, CallableAfter&& post) const
      {
          LOCK(cs_vNodes);
          for (auto&& node : vNodes) {
              if (NodeFullyConnected(node))
                  pre(node);
          }
          post();
      };
  
      // Addrman functions
      size_t GetAddressCount() const;
      void SetServices(const CService &addr, ServiceFlags nServices);
      void MarkAddressGood(const CAddress& addr);
      void AddNewAddresses(const std::vector<CAddress>& vAddr, const CAddress& addrFrom, int64_t nTimePenalty = 0);
      std::vector<CAddress> GetAddresses();
  
      // This allows temporarily exceeding m_max_outbound_full_relay, with the goal of finding
      // a peer that is better than all our current peers.
      void SetTryNewOutboundPeer(bool flag);
      bool GetTryNewOutboundPeer();
  
      // Return the number of outbound peers we have in excess of our target (eg,
      // if we previously called SetTryNewOutboundPeer(true), and have since set
      // to false, we may have extra peers that we wish to disconnect). This may
      // return a value less than (num_outbound_connections - num_outbound_slots)
      // in cases where some outbound connections are not yet fully connected, or
      // not yet fully disconnected.
      int GetExtraOutboundCount();
  
      bool AddNode(const std::string& node);
      bool RemoveAddedNode(const std::string& node);
      std::vector<AddedNodeInfo> GetAddedNodeInfo();
  
      size_t GetNodeCount(NumConnections num);
      void GetNodeStats(std::vector<CNodeStats>& vstats);
      bool DisconnectNode(const std::string& node);
      bool DisconnectNode(const CSubNet& subnet);
      bool DisconnectNode(const CNetAddr& addr);
      bool DisconnectNode(NodeId id);
  
      //! Used to convey which local services we are offering peers during node
      //! connection.
      //!
      //! The data returned by this is used in CNode construction,
      //! which is used to advertise which services we are offering
      //! that peer during `net_processing.cpp:PushNodeVersion()`.
      ServiceFlags GetLocalServices() const;
  
      //!set the max outbound target in bytes
      void SetMaxOutboundTarget(uint64_t limit);
      uint64_t GetMaxOutboundTarget();
  
      //!set the timeframe for the max outbound target
      void SetMaxOutboundTimeframe(uint64_t timeframe);
      uint64_t GetMaxOutboundTimeframe();
  
      //! check if the outbound target is reached
      //! if param historicalBlockServingLimit is set true, the function will
      //! response true if the limit for serving historical blocks has been reached
      bool OutboundTargetReached(bool historicalBlockServingLimit);
  
      //! response the bytes left in the current max outbound cycle
      //! in case of no limit, it will always response 0
      uint64_t GetOutboundTargetBytesLeft();
  
      //! response the time in second left in the current max outbound cycle
      //! in case of no limit, it will always response 0
      uint64_t GetMaxOutboundTimeLeftInCycle();
  
      uint64_t GetTotalBytesRecv();
      uint64_t GetTotalBytesSent();
  
      void SetBestHeight(int height);
      int GetBestHeight() const;
  
      /** Get a unique deterministic randomizer. */
      CSipHasher GetDeterministicRandomizer(uint64_t id) const;
  
      unsigned int GetReceiveFloodSize() const;
  
      void WakeMessageHandler();
  
      /** Attempts to obfuscate tx time through exponentially distributed emitting.
          Works assuming that a single interval is used.
          Variable intervals will result in privacy decrease.
      */
      int64_t PoissonNextSendInbound(int64_t now, int average_interval_seconds);
  
      void SetAsmap(std::vector<bool> asmap) { addrman.m_asmap = std::move(asmap); }
  
  private:
      struct ListenSocket {
      public:
          SOCKET socket;
          inline void AddSocketPermissionFlags(NetPermissionFlags& flags) const { NetPermissions::AddFlag(flags, m_permissions); }
          ListenSocket(SOCKET socket_, NetPermissionFlags permissions_) : socket(socket_), m_permissions(permissions_) {}
      private:
          NetPermissionFlags m_permissions;
      };
  
      bool BindListenPort(const CService& bindAddr, bilingual_str& strError, NetPermissionFlags permissions);
      bool Bind(const CService& addr, unsigned int flags, NetPermissionFlags permissions);
      bool InitBinds(const std::vector<CService>& binds, const std::vector<NetWhitebindPermissions>& whiteBinds);
      void ThreadOpenAddedConnections();
      void AddOneShot(const std::string& strDest);
      void ProcessOneShot();
      void ThreadOpenConnections(std::vector<std::string> connect);
      void ThreadMessageHandler();
      void AcceptConnection(const ListenSocket& hListenSocket);
      void DisconnectNodes();
      void NotifyNumConnectionsChanged();
      void InactivityCheck(CNode *pnode);
      bool GenerateSelectSet(std::set<SOCKET> &recv_set, std::set<SOCKET> &send_set, std::set<SOCKET> &error_set);
      void SocketEvents(std::set<SOCKET> &recv_set, std::set<SOCKET> &send_set, std::set<SOCKET> &error_set);
      void SocketHandler();
      void ThreadSocketHandler();
      void ThreadDNSAddressSeed();
  
      uint64_t CalculateKeyedNetGroup(const CAddress& ad) const;
  
      CNode* FindNode(const CNetAddr& ip);
      CNode* FindNode(const CSubNet& subNet);
      CNode* FindNode(const std::string& addrName);
      CNode* FindNode(const CService& addr);
  
      bool AttemptToEvictConnection();
      CNode* ConnectNode(CAddress addrConnect, const char *pszDest, bool fCountFailure, bool manual_connection, bool block_relay_only);
      void AddWhitelistPermissionFlags(NetPermissionFlags& flags, const CNetAddr &addr) const;
  
      void DeleteNode(CNode* pnode);
  
      NodeId GetNewNodeId();
  
      size_t SocketSendData(CNode *pnode) const;
      void DumpAddresses();
  
      // Network stats
      void RecordBytesRecv(uint64_t bytes);
      void RecordBytesSent(uint64_t bytes);
  
      // Whether the node should be passed out in ForEach* callbacks
      static bool NodeFullyConnected(const CNode* pnode);
  
      // Network usage totals
      RecursiveMutex cs_totalBytesRecv;
      RecursiveMutex cs_totalBytesSent;
      uint64_t nTotalBytesRecv GUARDED_BY(cs_totalBytesRecv) {0};
      uint64_t nTotalBytesSent GUARDED_BY(cs_totalBytesSent) {0};
  
      // outbound limit & stats
      uint64_t nMaxOutboundTotalBytesSentInCycle GUARDED_BY(cs_totalBytesSent);
      uint64_t nMaxOutboundCycleStartTime GUARDED_BY(cs_totalBytesSent);
      uint64_t nMaxOutboundLimit GUARDED_BY(cs_totalBytesSent);
      uint64_t nMaxOutboundTimeframe GUARDED_BY(cs_totalBytesSent);
  
      // P2P timeout in seconds
      int64_t m_peer_connect_timeout;
  
      // Whitelisted ranges. Any node connecting from these is automatically
      // whitelisted (as well as those connecting to whitelisted binds).
      std::vector<NetWhitelistPermissions> vWhitelistedRange;
  
      unsigned int nSendBufferMaxSize{0};
      unsigned int nReceiveFloodSize{0};
  
      std::vector<ListenSocket> vhListenSocket;
      std::atomic<bool> fNetworkActive{true};
      bool fAddressesInitialized{false};
      CAddrMan addrman;
      std::deque<std::string> vOneShots GUARDED_BY(cs_vOneShots);
      RecursiveMutex cs_vOneShots;
      std::vector<std::string> vAddedNodes GUARDED_BY(cs_vAddedNodes);
      RecursiveMutex cs_vAddedNodes;
      std::vector<CNode*> vNodes GUARDED_BY(cs_vNodes);
      std::list<CNode*> vNodesDisconnected;
      mutable RecursiveMutex cs_vNodes;
      std::atomic<NodeId> nLastNodeId{0};
      unsigned int nPrevNodeCount{0};
  
      /**
       * Services this instance offers.
       *
       * This data is replicated in each CNode instance we create during peer
       * connection (in ConnectNode()) under a member also called
       * nLocalServices.
       *
       * This data is not marked const, but after being set it should not
       * change. See the note in CNode::nLocalServices documentation.
       *
       * \sa CNode::nLocalServices
       */
      ServiceFlags nLocalServices;
  
      std::unique_ptr<CSemaphore> semOutbound;
      std::unique_ptr<CSemaphore> semAddnode;
      int nMaxConnections;
  
      // How many full-relay (tx, block, addr) outbound peers we want
      int m_max_outbound_full_relay;
  
      // How many block-relay only outbound peers we want
      // We do not relay tx or addr messages with these peers
      int m_max_outbound_block_relay;
  
      int nMaxAddnode;
      int nMaxFeeler;
      int m_max_outbound;
      bool m_use_addrman_outgoing;
      std::atomic<int> nBestHeight;
      CClientUIInterface* clientInterface;
      NetEventsInterface* m_msgproc;
      BanMan* m_banman;
  
      /** SipHasher seeds for deterministic randomness */
      const uint64_t nSeed0, nSeed1;
  
      /** flag for waking the message processor. */
      bool fMsgProcWake;
  
      std::condition_variable condMsgProc;
      Mutex mutexMsgProc;
      std::atomic<bool> flagInterruptMsgProc{false};
  
      CThreadInterrupt interruptNet;
  
      std::thread threadDNSAddressSeed;
      std::thread threadSocketHandler;
      std::thread threadOpenAddedConnections;
      std::thread threadOpenConnections;
      std::thread threadMessageHandler;
  
      /** flag for deciding to connect to an extra outbound peer,
       *  in excess of m_max_outbound_full_relay
       *  This takes the place of a feeler connection */
      std::atomic_bool m_try_another_outbound_peer;
  
      std::atomic<int64_t> m_next_send_inv_to_incoming{0};
  
      friend struct CConnmanTest;
      friend struct ConnmanTestMsg;
  };
  void Discover();
  void StartMapPort();
  void InterruptMapPort();
  void StopMapPort();
  unsigned short GetListenPort();
  
  struct CombinerAll
  {
      typedef bool result_type;
  
      template<typename I>
      bool operator()(I first, I last) const
      {
          while (first != last) {
              if (!(*first)) return false;
              ++first;
          }
          return true;
      }
  };
  
  /**
   * Interface for message handling
   */
  class NetEventsInterface
  {
  public:
      virtual bool ProcessMessages(CNode* pnode, std::atomic<bool>& interrupt) = 0;
      virtual bool SendMessages(CNode* pnode) = 0;
      virtual void InitializeNode(CNode* pnode) = 0;
      virtual void FinalizeNode(NodeId id, bool& update_connection_time) = 0;
  
  protected:
      /**
       * Protected destructor so that instances can only be deleted by derived classes.
       * If that restriction is no longer desired, this should be made public and virtual.
       */
      ~NetEventsInterface() = default;
  };
  
  enum
  {
      LOCAL_NONE,   // unknown
      LOCAL_IF,     // address a local interface listens on
      LOCAL_BIND,   // address explicit bound to
      LOCAL_UPNP,   // address reported by UPnP
      LOCAL_MANUAL, // address explicitly specified (-externalip=)
  
      LOCAL_MAX
  };
  
  bool IsPeerAddrLocalGood(CNode *pnode);
  void AdvertiseLocal(CNode *pnode);
  
  /**
   * Mark a network as reachable or unreachable (no automatic connects to it)
   * @note Networks are reachable by default
   */
  void SetReachable(enum Network net, bool reachable);
  /** @returns true if the network is reachable, false otherwise */
  bool IsReachable(enum Network net);
  /** @returns true if the address is in a reachable network, false otherwise */
  bool IsReachable(const CNetAddr& addr);
  
  bool AddLocal(const CService& addr, int nScore = LOCAL_NONE);
  bool AddLocal(const CNetAddr& addr, int nScore = LOCAL_NONE);
  void RemoveLocal(const CService& addr);
  bool SeenLocal(const CService& addr);
  bool IsLocal(const CService& addr);
  bool GetLocal(CService &addr, const CNetAddr *paddrPeer = nullptr);
  CAddress GetLocalAddress(const CNetAddr *paddrPeer, ServiceFlags nLocalServices);
  
  
  extern bool fDiscover;
  extern bool fListen;
  extern bool g_relay_txes;
  
  /** Subversion as sent to the P2P network in `version` messages */
  extern std::string strSubVersion;
  
  struct LocalServiceInfo {
      int nScore;
      int nPort;
  };
  
  extern RecursiveMutex cs_mapLocalHost;
  extern std::map<CNetAddr, LocalServiceInfo> mapLocalHost GUARDED_BY(cs_mapLocalHost);
  
  extern const std::string NET_MESSAGE_COMMAND_OTHER;
  typedef std::map<std::string, uint64_t> mapMsgCmdSize; //command, total bytes
  
  class CNodeStats
  {
  public:
      NodeId nodeid;
      ServiceFlags nServices;
      bool fRelayTxes;
      int64_t nLastSend;
      int64_t nLastRecv;
      int64_t nTimeConnected;
      int64_t nTimeOffset;
      std::string addrName;
      int nVersion;
      std::string cleanSubVer;
      bool fInbound;
      bool m_manual_connection;
      int nStartingHeight;
      uint64_t nSendBytes;
      mapMsgCmdSize mapSendBytesPerMsgCmd;
      uint64_t nRecvBytes;
      mapMsgCmdSize mapRecvBytesPerMsgCmd;
      NetPermissionFlags m_permissionFlags;
      bool m_legacyWhitelisted;
      int64_t m_ping_usec;
      int64_t m_ping_wait_usec;
      int64_t m_min_ping_usec;
      CAmount minFeeFilter;
      // Our address, as reported by the peer
      std::string addrLocal;
      // Address of this peer
      CAddress addr;
      // Bind address of our side of the connection
      CAddress addrBind;
      uint32_t m_mapped_as;
  };
  
  
  
  /** Transport protocol agnostic message container.
   * Ideally it should only contain receive time, payload,
   * command and size.
   */
  class CNetMessage {
  public:
      CDataStream m_recv;                  // received message data
      int64_t m_time = 0;                  // time (in microseconds) of message receipt.
      bool m_valid_netmagic = false;
      bool m_valid_header = false;
      bool m_valid_checksum = false;
      uint32_t m_message_size = 0;         // size of the payload
      uint32_t m_raw_message_size = 0;     // used wire size of the message (including header/checksum)
      std::string m_command;
  
      CNetMessage(CDataStream&& recv_in) : m_recv(std::move(recv_in)) {}
  
      void SetVersion(int nVersionIn)
      {
          m_recv.SetVersion(nVersionIn);
      }
  };
  
  /** The TransportDeserializer takes care of holding and deserializing the
   * network receive buffer. It can deserialize the network buffer into a
   * transport protocol agnostic CNetMessage (command & payload)
   */
  class TransportDeserializer {
  public:
      // returns true if the current deserialization is complete
      virtual bool Complete() const = 0;
      // set the serialization context version
      virtual void SetVersion(int version) = 0;
      // read and deserialize data
      virtual int Read(const char *data, unsigned int bytes) = 0;
      // decomposes a message from the context
      virtual CNetMessage GetMessage(const CMessageHeader::MessageStartChars& message_start, int64_t time) = 0;
      virtual ~TransportDeserializer() {}
  };
  
  class V1TransportDeserializer final : public TransportDeserializer
  {
  private:
      mutable CHash256 hasher;
      mutable uint256 data_hash;
      bool in_data;                   // parsing header (false) or data (true)
      CDataStream hdrbuf;             // partially received header
      CMessageHeader hdr;             // complete header
      CDataStream vRecv;              // received message data
      unsigned int nHdrPos;
      unsigned int nDataPos;
  
      const uint256& GetMessageHash() const;
      int readHeader(const char *pch, unsigned int nBytes);
      int readData(const char *pch, unsigned int nBytes);
  
      void Reset() {
          vRecv.clear();
          hdrbuf.clear();
          hdrbuf.resize(24);
          in_data = false;
          nHdrPos = 0;
          nDataPos = 0;
          data_hash.SetNull();
          hasher.Reset();
      }
  
  public:
  
      V1TransportDeserializer(const CMessageHeader::MessageStartChars& pchMessageStartIn, int nTypeIn, int nVersionIn) : hdrbuf(nTypeIn, nVersionIn), hdr(pchMessageStartIn), vRecv(nTypeIn, nVersionIn) {
          Reset();
      }
  
      bool Complete() const override
      {
          if (!in_data)
              return false;
          return (hdr.nMessageSize == nDataPos);
      }
      void SetVersion(int nVersionIn) override
      {
          hdrbuf.SetVersion(nVersionIn);
          vRecv.SetVersion(nVersionIn);
      }
      int Read(const char *pch, unsigned int nBytes) override {
          int ret = in_data ? readData(pch, nBytes) : readHeader(pch, nBytes);
          if (ret < 0) Reset();
          return ret;
      }
      CNetMessage GetMessage(const CMessageHeader::MessageStartChars& message_start, int64_t time) override;
  };
  
  /** The TransportSerializer prepares messages for the network transport
   */
  class TransportSerializer {
  public:
      // prepare message for transport (header construction, error-correction computation, payload encryption, etc.)
      virtual void prepareForTransport(CSerializedNetMsg& msg, std::vector<unsigned char>& header) = 0;
      virtual ~TransportSerializer() {}
  };
  
  class V1TransportSerializer  : public TransportSerializer {
  public:
      void prepareForTransport(CSerializedNetMsg& msg, std::vector<unsigned char>& header) override;
  };
  
  /** Information about a peer */
  class CNode
  {
      friend class CConnman;
      friend struct ConnmanTestMsg;
  
  public:
      std::unique_ptr<TransportDeserializer> m_deserializer;
      std::unique_ptr<TransportSerializer> m_serializer;
  
      // socket
      std::atomic<ServiceFlags> nServices{NODE_NONE};
      SOCKET hSocket GUARDED_BY(cs_hSocket);
      size_t nSendSize{0}; // total size of all vSendMsg entries
      size_t nSendOffset{0}; // offset inside the first vSendMsg already sent
      uint64_t nSendBytes GUARDED_BY(cs_vSend){0};
      std::deque<std::vector<unsigned char>> vSendMsg GUARDED_BY(cs_vSend);
      RecursiveMutex cs_vSend;
      RecursiveMutex cs_hSocket;
      RecursiveMutex cs_vRecv;
  
      RecursiveMutex cs_vProcessMsg;
      std::list<CNetMessage> vProcessMsg GUARDED_BY(cs_vProcessMsg);
      size_t nProcessQueueSize{0};
  
      RecursiveMutex cs_sendProcessing;
  
      std::deque<CInv> vRecvGetData;
      uint64_t nRecvBytes GUARDED_BY(cs_vRecv){0};
      std::atomic<int> nRecvVersion{INIT_PROTO_VERSION};
  
      std::atomic<int64_t> nLastSend{0};
      std::atomic<int64_t> nLastRecv{0};
      const int64_t nTimeConnected;
      std::atomic<int64_t> nTimeOffset{0};
      // Address of this peer
      const CAddress addr;
      // Bind address of our side of the connection
      const CAddress addrBind;
      std::atomic<int> nVersion{0};
      RecursiveMutex cs_SubVer;
      /**
       * cleanSubVer is a sanitized string of the user agent byte array we read
       * from the wire. This cleaned string can safely be logged or displayed.
       */
      std::string cleanSubVer GUARDED_BY(cs_SubVer){};
      bool m_prefer_evict{false}; // This peer is preferred for eviction.
      bool HasPermission(NetPermissionFlags permission) const {
          return NetPermissions::HasFlag(m_permissionFlags, permission);
      }
      // This boolean is unusued in actual processing, only present for backward compatibility at RPC/QT level
      bool m_legacyWhitelisted{false};
      bool fFeeler{false}; // If true this node is being used as a short lived feeler.
      bool fOneShot{false};
      bool m_manual_connection{false};
      bool fClient{false}; // set by version message
      bool m_limited_node{false}; //after BIP159, set by version message
      const bool fInbound;
      std::atomic_bool fSuccessfullyConnected{false};
      // Setting fDisconnect to true will cause the node to be disconnected the
      // next time DisconnectNodes() runs
      std::atomic_bool fDisconnect{false};
      bool fSentAddr{false};
      CSemaphoreGrant grantOutbound;
      std::atomic<int> nRefCount{0};
  
      const uint64_t nKeyedNetGroup;
      std::atomic_bool fPauseRecv{false};
      std::atomic_bool fPauseSend{false};
  
  protected:
      mapMsgCmdSize mapSendBytesPerMsgCmd;
      mapMsgCmdSize mapRecvBytesPerMsgCmd GUARDED_BY(cs_vRecv);
  
  public:
      uint256 hashContinue;
      std::atomic<int> nStartingHeight{-1};
  
      // flood relay
      std::vector<CAddress> vAddrToSend;
      const std::unique_ptr<CRollingBloomFilter> m_addr_known;
      bool fGetAddr{false};
      std::chrono::microseconds m_next_addr_send GUARDED_BY(cs_sendProcessing){0};
      std::chrono::microseconds m_next_local_addr_send GUARDED_BY(cs_sendProcessing){0};
  
      bool IsAddrRelayPeer() const { return m_addr_known != nullptr; }
  
      // List of block ids we still have announce.
      // There is no final sorting before sending, as they are always sent immediately
      // and in the order requested.
      std::vector<uint256> vInventoryBlockToSend GUARDED_BY(cs_inventory);
      RecursiveMutex cs_inventory;
  
      struct TxRelay {
          mutable RecursiveMutex cs_filter;
          // We use fRelayTxes for two purposes -
          // a) it allows us to not relay tx invs before receiving the peer's version message
          // b) the peer may tell us in its version message that we should not relay tx invs
          //    unless it loads a bloom filter.
          bool fRelayTxes GUARDED_BY(cs_filter){false};
          std::unique_ptr<CBloomFilter> pfilter PT_GUARDED_BY(cs_filter) GUARDED_BY(cs_filter){nullptr};
  
          mutable RecursiveMutex cs_tx_inventory;
          CRollingBloomFilter filterInventoryKnown GUARDED_BY(cs_tx_inventory){50000, 0.000001};
          // Set of transaction ids we still have to announce.
          // They are sorted by the mempool before relay, so the order is not important.
          std::set<uint256> setInventoryTxToSend;
          // Used for BIP35 mempool sending
          bool fSendMempool GUARDED_BY(cs_tx_inventory){false};
          // Last time a "MEMPOOL" request was serviced.
          std::atomic<std::chrono::seconds> m_last_mempool_req{std::chrono::seconds{0}};
          std::chrono::microseconds nNextInvSend{0};
  
          RecursiveMutex cs_feeFilter;
          // Minimum fee rate with which to filter inv's to this node
          CAmount minFeeFilter GUARDED_BY(cs_feeFilter){0};
          CAmount lastSentFeeFilter{0};
          int64_t nextSendTimeFeeFilter{0};
      };
  
      // m_tx_relay == nullptr if we're not relaying transactions with this peer
      std::unique_ptr<TxRelay> m_tx_relay;
  
      // Used for headers announcements - unfiltered blocks to relay
      std::vector<uint256> vBlockHashesToAnnounce GUARDED_BY(cs_inventory);
  
      // Block and TXN accept times
      std::atomic<int64_t> nLastBlockTime{0};
      std::atomic<int64_t> nLastTXTime{0};
  
      // Ping time measurement:
      // The pong reply we're expecting, or 0 if no pong expected.
      std::atomic<uint64_t> nPingNonceSent{0};
      // Time (in usec) the last ping was sent, or 0 if no ping was ever sent.
      std::atomic<int64_t> nPingUsecStart{0};
      // Last measured round-trip time.
      std::atomic<int64_t> nPingUsecTime{0};
      // Best measured round-trip time.
      std::atomic<int64_t> nMinPingUsecTime{std::numeric_limits<int64_t>::max()};
      // Whether a ping is requested.
      std::atomic<bool> fPingQueued{false};
  
      std::set<uint256> orphan_work_set;
  
      CNode(NodeId id, ServiceFlags nLocalServicesIn, int nMyStartingHeightIn, SOCKET hSocketIn, const CAddress &addrIn, uint64_t nKeyedNetGroupIn, uint64_t nLocalHostNonceIn, const CAddress &addrBindIn, const std::string &addrNameIn = "", bool fInboundIn = false, bool block_relay_only = false);
      ~CNode();
      CNode(const CNode&) = delete;
      CNode& operator=(const CNode&) = delete;
  
  private:
      const NodeId id;
      const uint64_t nLocalHostNonce;
  
      //! Services offered to this peer.
      //!
      //! This is supplied by the parent CConnman during peer connection
      //! (CConnman::ConnectNode()) from its attribute of the same name.
      //!
      //! This is const because there is no protocol defined for renegotiating
      //! services initially offered to a peer. The set of local services we
      //! offer should not change after initialization.
      //!
      //! An interesting example of this is NODE_NETWORK and initial block
      //! download: a node which starts up from scratch doesn't have any blocks
      //! to serve, but still advertises NODE_NETWORK because it will eventually
      //! fulfill this role after IBD completes. P2P code is written in such a
      //! way that it can gracefully handle peers who don't make good on their
      //! service advertisements.
      const ServiceFlags nLocalServices;
  
      const int nMyStartingHeight;
      int nSendVersion{0};
      NetPermissionFlags m_permissionFlags{ PF_NONE };
      std::list<CNetMessage> vRecvMsg;  // Used only by SocketHandler thread
  
      mutable RecursiveMutex cs_addrName;
      std::string addrName GUARDED_BY(cs_addrName);
  
      // Our address, as reported by the peer
      CService addrLocal GUARDED_BY(cs_addrLocal);
      mutable RecursiveMutex cs_addrLocal;
  public:
  
      NodeId GetId() const {
          return id;
      }
  
      uint64_t GetLocalNonce() const {
          return nLocalHostNonce;
      }
  
      int GetMyStartingHeight() const {
          return nMyStartingHeight;
      }
  
      int GetRefCount() const
      {
          assert(nRefCount >= 0);
          return nRefCount;
      }
  
      bool ReceiveMsgBytes(const char *pch, unsigned int nBytes, bool& complete);
  
      void SetRecvVersion(int nVersionIn)
      {
          nRecvVersion = nVersionIn;
      }
      int GetRecvVersion() const
      {
          return nRecvVersion;
      }
      void SetSendVersion(int nVersionIn);
      int GetSendVersion() const;
  
      CService GetAddrLocal() const;
      //! May not be called more than once
      void SetAddrLocal(const CService& addrLocalIn);
  
      CNode* AddRef()
      {
          nRefCount++;
          return this;
      }
  
      void Release()
      {
          nRefCount--;
      }
  
  
  
      void AddAddressKnown(const CAddress& _addr)
      {
          assert(m_addr_known);
          m_addr_known->insert(_addr.GetKey());
      }
  
      void PushAddress(const CAddress& _addr, FastRandomContext &insecure_rand)
      {
          // Known checking here is only to save space from duplicates.
          // SendMessages will filter it again for knowns that were added
          // after addresses were pushed.
          assert(m_addr_known);
          if (_addr.IsValid() && !m_addr_known->contains(_addr.GetKey())) {
              if (vAddrToSend.size() >= MAX_ADDR_TO_SEND) {
                  vAddrToSend[insecure_rand.randrange(vAddrToSend.size())] = _addr;
              } else {
                  vAddrToSend.push_back(_addr);
              }
          }
      }
  
  
      void AddInventoryKnown(const CInv& inv)
      {
          if (m_tx_relay != nullptr) {
              LOCK(m_tx_relay->cs_tx_inventory);
              m_tx_relay->filterInventoryKnown.insert(inv.hash);
          }
      }
  
      void PushInventory(const CInv& inv)
      {
          if (inv.type == MSG_TX && m_tx_relay != nullptr) {
              LOCK(m_tx_relay->cs_tx_inventory);
              if (!m_tx_relay->filterInventoryKnown.contains(inv.hash)) {
                  m_tx_relay->setInventoryTxToSend.insert(inv.hash);
              }
          } else if (inv.type == MSG_BLOCK) {
              LOCK(cs_inventory);
              vInventoryBlockToSend.push_back(inv.hash);
          }
      }
  
      void PushBlockHash(const uint256 &hash)
      {
          LOCK(cs_inventory);
          vBlockHashesToAnnounce.push_back(hash);
      }
  
      void CloseSocketDisconnect();
  
      void copyStats(CNodeStats &stats, const std::vector<bool> &m_asmap);
  
      ServiceFlags GetLocalServices() const
      {
          return nLocalServices;
      }
  
      std::string GetAddrName() const;
      //! Sets the addrName only if it was not previously set
      void MaybeSetAddrName(const std::string& addrNameIn);
  };
  
  /** Return a timestamp in the future (in microseconds) for exponentially distributed events. */
  int64_t PoissonNextSend(int64_t now, int average_interval_seconds);
  
  /** Wrapper to return mockable type */
  inline std::chrono::microseconds PoissonNextSend(std::chrono::microseconds now, std::chrono::seconds average_interval)
  {
      return std::chrono::microseconds{PoissonNextSend(now.count(), average_interval.count())};
  }
  
  #endif // BITCOIN_NET_H
  